#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<assert.h>
char* my_strncat(char* s1, const char* s2, int num)
{
	assert(s1 && s2);
	char* ret = s1;
	while (*s1 != '\0')
	{
		s1++;
	}
	while (num--)
	{
		*s1++ = *s2++;
	}
	return ret;
}
int main()
{
	char arr1[20] = "abc";
	char arr2[20] = "def";
	char* ps = my_strncat(arr1, arr2, 2);
	printf("%s\n", ps);
	return 0;
}